Explain the physiological effects of ABA.

Explanation

It helps in reducing transpiration rate by closing stomata. It inhibits K+ uptake by guard cells and promotes the leakage of malic acid. It results in closure of stomata.
It spoils chlorophylls, proteins and nucleic acids of leaves making them yellow
Inhibition of cell division and cell elongation.
ABA is a powerful growth inhibitor. It causes 50% inhibition of growth in Oat coleoptile .
It induces bud and seed dormancy.
It promotes the abscission of leaves, flowers and fruits by forming abscission layers.
ABA plays an important role in plants during water stress and during drought conditions. It results in loss of turgor and closure of stomata .
It has anti-auxin and anti-gibberellin property
Abscisic acid promotes senescence in leaves by causing loss of chlorophyll pigment decreasing the rate of photosynthesis and changing the rate of proteins and nucleic acid synthesis.